Cleanup python version properties

Now that python 2 is fully removed, there's no need for
version-specific properties. Remove them.

Also remove usages of embedded_launcher: true, as that
is the new default value.

Bug: 399954452
Test: Presubmits
Change-Id: I8a0861c6f336f414cdc064e21c3c7eda6e251dc5
1 file changed